Auditory and Vestibular System

Question 1

Presbycusis

Answer 1

-high frequency hearing loss with aging

Question 2

Basilar membrane is ________ organized.

Answer 2

-tonotopically (spatial arrangement of where sounds of different frequency are processed in the brain)

Question 3

Outer hair cells are embedded in the ________ membrane.

Answer 3

-tectoral

Question 4

3 Types of Hearing Loss

Answer 4

1. conductive
2. sensory
3. neural

Question 5

Sensorineural Hearing Loss

Answer 5

• common
• damage to outer hair cells due to noise exposure
• can also be caused by ototoxic drugs
• weber test: localizes to unaffected ear
• rinne test: normal (air > bone)
• severe sensorineural hearing loss -> cochlear implant
• caused by loss of endocochlear potential

Question 6

Meneiers Disease

Answer 6

• fluctuating low frequency hearing loss
• problem with fluid composition and pressure of fluids in cochlea
• tinnitus

Question 7

CN 8 Fibers

Answer 7

Type 1: myelinated, large, 95% of total, mian ascending neurons for audition, innervate inner hair cells

Type 2: 5%, unmyelinated, function unknown, innervate outer hair cells, respond to loud sounds

Question 8

Otoacustic Emissions

Answer 8

• can record sound coming out of ear

- way to test if auditory system is functional

Question 9

Phase Locking

Answer 9

• nerve doesn’t fire for every cycle of cilia movement but does fire at specific point in cycle
• low frequency neurons exhibit phase locking to sounds
• phase locking limit is 1500 Hz

Question 10

Interaural Level Distances (ILDs)

Answer 10

• created at high frequencies (>1500Hz) where head casts an acoustic shadow
• encoded in lateral sup. olive (LSO)

Question 11

3 Main Acoustical Cues to Location

Answer 11

1. interaural time delay (ITD)
2. interaural level differences (ILD)
3. spectral cues (>5kHz)

Question 12

Interaural Time Delay

Answer 12

• requires that inputs to medial sup. olive (MSO) neurons exhibit phase locking to sounds
• important for low frequency

Question 13

Inferior colliculus responds to ______ acoustic space.

Answer 13

-contralateral

Question 14

Medial Genticulate Nucleus

Answer 14

• projects to amygdala

- auditory fear conditioning

Question 15

Broca’s Area

Answer 15

-44, 45

Question 16

Wernicke’s Area

Answer 16

-22

Question 17

Vestibular System

Answer 17

• provides sense of equilibrium
• located in temporal bone
• hair cells in otolith organs respond to linear accelerations of head
• hair cells in amullae respond to head rotations

Question 18

Endolymph

Answer 18

• high [K+]= 140 mM
• low [Na+], [Ca++]
• hair bundles project from the apical surface of hair cells into endolymph
• move the cupula and stimulates hair cells in crista ampullaris

Question 19

Perilymph

Answer 19

• basolateral hair cell membrane is bathed in perilymph
• low [K+]
• high [Na+] and [Ca++]

Question 20

Otoconia

Answer 20

-calcium carbonate crystals overlaying hair bundles

Question 21

Kinocilium

Answer 21

• tallest hair in bundle
• gives hair directional sensitivity
• movement toward kinocilium depolarizes cell and causes nerve excitation
• movement away from cell causes hyperpolarization

Question 22

Direction of Hairs in Utricle

Answer 22

-toward line of polarity

Question 23

Direction of Hairs in Sacule

Answer 23

-away from line of polarity

Question 24

Semicircular Canals

Answer 24

• hair bundles face same way

- sense rotation and active movement (not continuous rotation)

Question 25

Motion Sensed by Cupula

Answer 25

- acceleration - deceleration - does not sense continued motion

Question 26

Hair Cell MOA

Answer 26

- mechanotransducers - ion channels are gated by tip links, which connect to cilia in hair bundle - pushing hair bundle in excitatory direction opens channels and K+ and Ca++ from endolymph enter and depolarize hair cell - hair cell fires action potential

Question 27

Vestibular Nuclei

Answer 27

-subdivided into superior, medial, lateral, descending

Question 28

Vestibolar Ocular Reflex

Answer 28

- shortest reflex in body - enables stable visual field during head movement - leads to nystagmus

Question 29

Stapes bone connects to the ______ window.

Answer 29

- oval | - oval window of the cochlea

Question 30

Hair cells are located in:

Answer 30

-organ of chordi

Question 31

Cochlea

Answer 31

- apex (tip) processes low frequency sounds | - base processes high frequency sounds

Question 32

Treatment of Sensorineural Hearing Imparement

Answer 32

- air conduction hearing aids - implantable hearing aids - cochlear implants (1 year old) - assistive listening devices - speech and language training

Question 33

Conductive Hearing Loss

Answer 33

-Causes: otitis media (most common cause), TM perforation, cholesteatoma, otosclerosis, congenital aural atresia

Question 34

Sensory Hearing Loss

Answer 34

-Causes: hair cell loss (presbycusis, noise trauma, ototoxicity, genetic factors, endolymphatic hydrops, meniere's disease)

Question 35

Presbycusis

Answer 35

- gradual, progressive bilateral hearing loss caused by degenerative physiologic changes associated with aging - dec. ability to understand loud speech - dec. hearing threshold sensitivity

Question 36

Causes of Congenital Hearing Loss

Answer 36

- environmental (25%) | - genetic (50%) (connexin 26/GJB2 important gene)

Question 37

Neural Hearing Loss

Answer 37

- causes: 8th nerve tumors, auditory neuropathy, MS | - asymmetric hearing loss is red flag of CNS

Question 38

Vestibular Schwannoma

Answer 38

-headache occurs late in progression

Question 39

Meniere's Disease

Answer 39

-caused by excess endolymph fluid within inner ear

Question 40

Most Common Non-Genetic or Non-Congenital Cause of Hearing Loss

Answer 40

-cytomegalovirus (CMV)

Question 41

Cholesteatoma

Answer 41

-skin cysts that form due to retraction, most commonly in pars flaccida

Question 42

Otosclerosis

Answer 42

- localized disorder of bone remodeling - causes progressive conductive hearing loss - most common in Caucasians - tx: stapedectomy

Question 43

Lateral Sup. Olive

Answer 43

-receives ILDs

Question 44

Medial Sup. Olive

Answer 44

-interprets ITDs

Question 45

Unilateral Lesion of R Sup. Olive

Answer 45

-will affect sound localization (can't tell where sound is coming from)

Question 46

Inferior Colliculus

Answer 46

-encodes contralateral sound sources

Question 47

Otitis Media

Answer 47

-fluid has filled middle ear